Abstract: Failure of one or more battery cells, for example of an inverter battery bank, is detected by monitoring the second derivative of the curve U(t) representative of the voltage U at the terminals of the battery in the course of discharge. If the second derivative is positive, this is significant of a failure.

Abstract: The backup time of the battery is obtained by estimation, in iterative manner, of discharging of the battery during successive estimated time intervals. During each of the estimated time intervals, an estimated discharging current in terms of the actual discharge power, an estimated voltage, and an estimated state of charge are computed in accordance with a mathematical model equivalent to the battery. The backup time of the battery is equal to the sum of the estimated time intervals necessary for the estimated voltage to reach a preset threshold. The process enables ageing of the battery to be taken into account and an alarm to be provided when the lifetime of the battery becomes too short.